Oftel (or whoever they call themselves now) forbid BT Retail (the idiots with call centres) from getting priority service from BT Wholesale (the company that looks after the wires themselves).
On paper. I think the chinese walls have some holes in practice..... a leopard can't change its spots.
As for Oftel. Well, having read the news about their dodgy IT department, you can't help thinking what else is going on there.
And anyway, you're wrong... it's three main companies..... Retail, Wholesale and Openreach. The latter are the ones who do the access and backhaul. Wholesale provide structured products (e.g. IPStream a.k.a. ADSL) using Openreach assets to Retail and others (assuming those others are not building their own structured products from scratch LLU style and hence buying from Openreach). Hence it still remains one big trough for BT Plc to stick their greedy snout into.
You can't polish a turd as they say.... it's win win win for the BT Plc monopoly, no matter what Ofcom say as they've got no teeth having left their dentures at home.